Filtering unit



T. R. KoMLlNE July 21, 1959 FILTERING UNIT Filed Dec. 12. 1955 5 Sheets-Sheet 1 SWU MTII.- NN

NCQ.

July 21, 1959 T. R. KOMLINE FILTERING UNIT 5 Sheets-Sheet 2 Filed Deo. 12. 1955 INVENTOR :15mn/v /Q/fm/'nu ATTORNEY;

July 21, 1959 T. R. KOMUNE 2,895,614

FILTERING UNIT Filed Dec. l2, 1955 f 5 Sheetsheet 3 N INVENTOR i mm ema-e BY W10/ZQMMM ATTORNEYS' FILTEG UNIT Thomas R. Komline, Gladstone, NJ., assignor to Komline-Sanderson Engineering Corporation, Peapack, NJ., a corporation of New Jersey Application December 12, 1955, Serial No. 552,325 12 Claims. (Cl. Z110-401) This invention relates to a filtering unit of the endless belt type wherein a series of air pressure modifying means in substantially fluid-tight sealing engagement with a movable filter media function to create differential air pressures on opposite sides of the media 'to force liquids therethrough from a mixture of liquid and solid materials in Contact with one face or `Surface of the media.

Generally, the air pressure modifying means assumes the form of a suction pan or box beneath one run of a continuously moving iilter belt to suck liquids through the belt from -a mixture of liquids and solids deposited on the upper surface thereof. It is, of course, necessary that suitable seals or gaskets be arranged to establish a substantially fluid-tight sealing relation between the belt and the suction box or other air pressure modifying means. It has been found that the movement of the belt prevents efficient functioning of the sealing means and tends to cause rapid wear and loss of efficiency of the sealing means in such an arrangement. In addition, the frictional engagement between the sealing means and the belt exerts a drag on the belt and increases the power requirements for causing such movement. Due to the rapid wear on the sealing means in such prior filtering units, such units have been operable only at low vacuum, have been subject to rapid loss of etiiciency and, generally speaking, have been impractical.

With the foregoing in mind, the present invention contemplates an improved form of endless belt-type filtering unit wherein ythe belt is moved intermittently and has a dwell between its movements, the suction or other air pressure-modifying action of the boxes being exerted on the belt during such dwells.

Where the box or boxes are employed to exert suction on the belt, the arrangement is such that the boxes are vented to the atmosphere or the suction is otherwise discontinued during the respective movements of the belt.

A further feature of the invention consists in providing a mechanism for moving said box or boxes out of sealing engagement with the belt during each period of belt movement.

While in 4the preferred embodiment of the invention the last mentioned feature is employed in conjunction with means for relieving the suction in the boxes and the combination of these two features constitutes a further novel aspect of the invention, the invention is of sufficient scope to cover either of the features when separately employed.

Considered from one aspect, the invention may utilize but a single such box. However, a further important feature of the invention consists in employing a series of the said boxes arranged in uniformly spaced relation along the belt, and in causing the successive movements of the belt to equal the distance between centers of the boxes so that each area of solid material or semi-solid material (generally known as the filter cake) deposited on the belt will be successively acted upon by each of '2,895,614 Patented July 21, 1959 the respective boxes as the belt moves to positions successively in registry with each.

Also included in the invention is a novel arrangement of mechanism for effecting coordinated automatic control of the intermittent belt movements, the movements to and from sealing engagement with the belt of the box or boxes, and/or the venting of the suction boxes to atmospheric pressure (where suction is applied to the belt through the boxes as distinguished from an air pressure in excess of atmospheric pressure applied lthrough the boxes against the side of the belt which is contacted by the liquid and solid containing material to be filtered).

The foregoing, as well as other incidental objects and advantages, are attained by the preferred embodiment of the invention illustrated in the accompanying drawings, in which:

Figure 1 is a side elevation of a filtering unit embodying the novel features of the invention;

Figure 2 is a plan view of the unit shown in Figure l;

Figure 3 is an enlarged fragmentary sectional view on the line 3-3 of Figure 2;

Figure 4 is a cross-section on the line 4-4 of Figure 3;

Figure 5 is an enlarged cross-section through the movable frames which raise and lower the suction boxes, showing the manner in which these frames are linked together. This View is taken on the line 5-5 of Figure 1;

Figure 6 is an enlarged diagrammatic lview of the control means for controlling and coordinating the actuation of the several parts of the unit;

Figure 7 is -a perspective View of one of the suction boxes; and

Figures 8 and 9, respectively, are enlarged views, partly in section, of the upper end portions of the piston rods and pawls which drive the filtering media intermittently.

Referring now in detail to the accompanying drawings, the filtering media 10 there shown is in the form of an endless belt of a suitable porous ltering material which is supported and guided for movement in an endless circuit around longitudinally spaced rollers 11 and 12, respectively. Roller 11 has its shaft 13 rotatably supported in a bearing block 14 carried by a supporting frame 1S of any usual or suitable construction. Similarly, a supporting frame 16 spaced longitudinally from the frame 15 carries laterally opposed bearings 17 which rotatably support the shaft 18 of roller 12. At longitudinally spaced intervals between the frames 15 and 16 are pairs of relatively spaced upright members 19 which are embedded in or otherwise rigidly fixed to supporting surface 20. Upper and lower rollers 22 and 23 (Figs. 2 and 3) rotatably journaled between the laterally opposed upright members 19 of each pair function to support the upper and lower runs 10a and 10b respectively of the belt against sagging. In the embodiment shown, it will be noted that the belt 10 is vertically inclined somewhat from the horizontal although it may be said to extend in a generally horizontal direction, and the upper run 10a of the belt, which constitutes the operative filtering run, moves from its lower end toward its upper discharge end over the roller 12. The means for effecting such movement will be described hereinafter. It will be obvious that solid materials remaining on the filtering inn 10a as said run moves over the roller 12 will be discharged from the belt. In order to facilitate such discharge it may be desirable, at least in filtering certain types of materials, to provide a conventional doctor blade or scraper 25 supported on the frame 16, as shown in Figures 1 and 2.

The mixture of liquid and solid materials to be filtered may be delivered through a pipe 27 from any suitable source into a feed hopper 28 supported by frame 15 over the lower end of the inclined operative run a of the belt. This hopper 28 is provided with laterally opposed sides ZiirziandA a rear end`wall' 2817 through which the pipe 27 delivers the material for filtering.A VThe operative belt run 10a, which is inisnug substantially huid-tight relation with the lower edges ofthe hopper sides and back wall; defines the bottom for the hopper and it will thus be'sen that the hopper will function to retain a supply of materialfor filtering over the-lower end of the inclined belt runflQa. Inv the illustrated embodiment', as best shown in Fig's. 3 and 4, a suitable Huid-tight engagement between the hopper 28 and ther belt is provided by forming the belt with a pair-'of laterally opposed ribs or seals 29 whichmove through grooves in the lower edges of the hopper side walls 28a while external and internal resilientf seals`30a= and-'30h' ('Fg. l) carried at the lower edge ofthe hopper rearV wall 28b, are in wiping engagement withfthe' upper surface of the belt between the sealing ribs 29. In order to permit them to properly accommodate the sealing ribs 29, the lower series of belt supporting rollers 23 may be provided with annular grooves 32 respectively for reception of the ribs 29.

One or more boxes 33 each having an open upper side directed toward the operative be'ltrun 10a are disposed for sealing-engagementwiththe belt run and to this end (and asshown'inFigs. 3 and 4) eachsuch box 33 is provided-witha suitableresilient'marginal seal or gasket 34 around its'open upper end. In the event but one box 33 is=provided, it will be'positioned at least partially in registry with the hopper 28. However, if more than one such box is provided, asin the-preferred embodiment, these-willV be uniformly shaped and relatively uniformly spaced along the belt with the iirst in series of these at the lower endof the' belt run 10a in registry or partial registry with the hopper 28, whereby such box may functionto draw or force liquid from the hopper contents throughl the belt and'form thereon alter cake or deposit of solid material.

Intermittent drive mechanism for driving the belt '10 in successive steps or increments equal to the distance betweencenters of adjoining boxes 33 is exemplitied by the ratchet wheel 35 (Fig. l) iixed on the shaft 18 of the roller 12 at the discharge end of the belt to transmit rotation'to the roller. This ratchet wheel is driven by pawls 36'fand 37 respectively, Vcarried by the reciprocating piston rods 38 and 39fof pistons (not shown), which in turn are disposed for reciprocation'in the respective cylinders 42 andfl: Each of these cylinder and piston units thus constitutes a hydraulic ram and is preferably of the doublet acting' type. In the'embodiment shown the said rams are adapted foi-'simultaneous actuation and the pawl 36'of the ram'V 40'is adapted for operative engagementwith wheel 35- on thefp'iston rod upstroke, while pawl 37V is disposed fo'rop'erative engagement with the ratchetwheel H ori=theensuing-downstroke of its piston rod 39. I

Thus',- as shown in Figure 8, the`pawl 36 is pivoted at 36afor free upward swinging'orretraction on its return stroke, but on its upward operative stroke is prevented from swingingdownwardly beyond operativel position by engagement ofl its stop portion 36b with piston rod 38.' The pawl 37,' -as-shown in Fig. 9, may constitute-'a detent which is'springprojected horizontally from a `socket member 4? carried by Ypiston rod 39, to thus be operative on the Vdown stroke 'of rod 39.`

ln'order to actuate the hydraulic rams for'intermittently'driving the belt 10 `the upper'endsl-o'ftheir respective' cylinders 42 and 43 are 'connected to branch lines or conduits-44' and-45 from a main hydraulic line 46, the arrngementbeing,such1that the lines-44, 45`v and'46 establish-communication betweenthe up'per ends of the said cylinders land afconventional reversing valve 47 ofv the rotary type which is mounted on a panel 48'supported' between adjoining upright's19: Similarly, -the lower/ends ofthe-respectiveramcylinders 42 and 43 communicate through lines 49, 50 and 51 with the said reversing valve 47 whereby the valve 47 may be positioned in usual manner to cause the hydraulic fluid to enter the said cylinders 42 and 43 through either end thereof and to be withdrawn from the other end.

As is best shown in Figure 6, the said reversing valve 47 has intake and return lines 53 and 54 respectively establishing communication between it and the hydraulic pump and reservoir units and 56. The arrangement is such that hydraulic iluid is delivered from the reservoir to the pump through a line 57, then delivered to the valve 4-'7 through the line 53 and eventually returned to the reservoir from the valve through the return line 54.

Associated with the respective boxes 33 is a suitable pneumatic means for modifying the air pressure within the boxes when the open sides of the boxes are sealed by engagement with the belt run 10a. It will be understood that the boxes are associated with the belt in such'a manner as to create differential air pressures on opposite sides of the operative belt'run ltla'for lurging uid through the belt.

in the preferred embodiment of the invention the boxes 33 are located beneath the operative belt run 10a for sealing engagement with the lower surface of this run and the pneumatic means is arranged to evacuate both air and liquid from the boxes and thus to suck'liquids through the belt from the mixture of liquids and solids deposited on the belt from the hopper 28.

Accordingly, and as shown in Figures l and 6, the pneumatic means is exemplified by a suction line 59 from a suitable evacuating means (not shown). This line S9 is adapted for communication through a valve 60 and line 61, with a header or manifold 62 (Fig. l) which in turn communicates with each of the boxes 33 through lines 63. lf desired the lines 63may be rigid metal pipes and may function to suitably support the manifold 62 for movement as a unit with the several boxes 33, and the suction line 59 may be tiexible to permit relative movement between the header 62 and valve 60.

From the foregoing it will be apparent that the boxes and their associated pneumatic means constitute apparatus for applying suction to areas of a similar size and shape along the belt. These areas will correspond in shape and size to the corresponding dimensions of the upwardly opening boxes or, in other words, to the mouths of the suction boxes 33. As has been mentioned earlier, important aspects of the invention reside in the concept of venting the suction boxes to atmospheric pressure during each of the successive intermittent movements of theV belt and/or of relatively moving the boxes and the belt to and from sealing engagement with each other in coordination with the intermittent belt movements. It is preferred to incorporate both of these functions in the unit of the invention, although the scope of the invention is believed such as to include a machine or unit utilizing either of these functions alone.

The means for venting the boxes 33 to the atmsphere may conveniently comprise the conventional twoway rotary valve 60 above referred to, which is interposed between the lines 59 and 61 leading to the header 62'so` that inone operative position it establishes communication between the suction line 59 and line 61 to the header and in its other operative position when rotated to 90 from the tirst position-it places'v the line 61; the header 629 and'boxes 33 in communication-with' the atmosphere through a suitable outlet 64.-

Inl order to provide for the relative movement between the boxes`33` and'the operative filtering run 10a of the belt so that these may be moved to and from sealing engagement'theboxes are carried by a suitable rgid'movabl'e frame 65 comprising the opposed side railsrigidly interconnected by cross pieces or lateral extensions 66 of the boxes which directly support the respective boxes 33. The frame is guided for vertical movementv toward and away from thev belt run 10a by ass-m14 angle brackets 67 iixed on the frame 65 in sliding engagement with the respective uprights 19.

Operative movement of the frame 65 in the present embodiment is produced through reciprocation of a rigid sliding frame 68 supported on slide bearings 69 for reciprocating movement generally parallel to the frame 65 and belt run 10a. The bearings 69 preferably are in the form of angle brackets rigidly secured in laterally opposed relation to the inner faces of the respective frame uprights 19. The sliding frame 68 is connected to the 'vertical moving frame 65 by a plurality of parallel toggle links 7l? which are normally vertically upwardly inclined toward the right, or upper end of the frame 65 so that movement of the reciprocating frame toward the right in Figure l will move these links 70 toward an erect or vertical position and thus raise the upper frame 65 and its associated boxes 33. However, it will be noted that the extent of movement of the frame 68 is such that the links 70 will never reach a fully erect or dead center position and thus will exert at all times a component of force tending to urge the vertical movable frame 65 toward the right. Consequently, the sliding guides 67 for the frame 65 need be but on the left side of the respective uprights 19 only. t

Movement of the sliding frame 68 for the purpose of raising and lowering the frame 65 is caused by doubleacting hydraulic rarn 72 (Figs. 1 and 6) having its cylinder portion fixed on a bracket 73 rigidly connected between laterally opposed uprights 19 and having the externally projecting end of its piston rod 74 connected to a cross beam 75 constituting a part of the frame 68. The ram 72 is basically of the same construction as the rams 42 and 43 earlier mentioned and actuating uid is supplied to and withdrawn from the opposite ends of its cylinder through hydraulic lines 76 and 77 from a reversing valve 78 which is similar in all respects to the reversing valve 47. Valve 78 also is mounted on the panel 48 and has supply and return lines 79 and 80 connecting it to the pump 55 and the reservoir 56 respectively. The valve 78 is operable in usual manner to direct fluid from the supply line 79 into either of the lines 76 or 77 leading to opposite ends of the ram 72, While at the same time connecting the other of said lines to the return line 80.

The several valves 60, 7 8 and 47 are mounted in alignment longitudinally of the panel 48 so that they may be actuated automatically in properly timed and coordinated relation to control the intermittent movements 'of the belt, the movements of the boxes to and from sealing engagement, and the venting of the boxes to the atmosphere. Preferably the arrangement is such that prior to each movement of the belt the suction to the boxes will be discontinued first to facilitate retraction of the boxes out of sealing engagement with the belt, the boxes will be retracted and the belt will move. At the conclusion of its movement the belt will dwell in its new position for a predetermined period and the boxes 33 will be moved back into sealing engagement with the belt and suction applied through them to draw liquid ltrate through the belt.

Various operating and coordinating mechanisms may be employed for this purpose though only one such mechanism is illustrated more or less diagrammatically in the accompanying drawings. In the exemplified arrangement, the valves 60, 78 and 47 are of the rotary type and all movable through a range of 90 of rotation from one opertaive position to the other. Fixed on the externally projecting actuating shafts of the respective valves 69, '78 and 47 are pinions 82, 83 and 84, respectively. Coacting with these pinions is a segmental rack bar 85 mounted in slide bearings 86 on the panel 48 for longitudinal reciprocation past the pinions. Toothed rack segments 82a, 83a and 84a are carried in spaced relation on the bar 85 for cooperation with the pinions 82, 83 and 84 in properly timedA and coordinated relation. Reciprocation of rack bar 84 is trans# mitted through a pitman 87 from a crank wheel 88 through an eccentrically located crank pin to which the pitman is connected. Wheel 88 is iixed on the output shaft of a reduction gear box 90 mounted on panel 48. Drive is imparted to the gear box 90 through the output shaft 91 of a conventional variable speed electrical motor 92, also mounted on panel 48, whereby the apparatus may be automatically operated at varying speeds through a continuous series of filtering cycles.

The location of the rack segments 82a, 83a and 84a is such that each will successively engage and actuate the pinions of their associated valves in the proper order during movement of the bar 85. The length or longitudinal extent of each such segment is such as will cause it to rotate its pinion and valve body through an angle of 90, or, in other words, from one operative position of the valve to the other alternate operative position thereof.

In Figures 1 and 3 of the drawings, the boxes 33 are lowered out of sealing engagement with operative belt run 10a. The belt at this time is midway through one increment of its movement and the valve 60 is positioned to vent the boxes 33 to the atmosphere while the valve 78 is positioned to maintain the boxes retracted from sealing engagement with the belt. At this time the rack bar is positioned to the left hand extremity of its range of reciprocating movement and the rack segment 84a has just positioned the valve 47 to project upwardly, the two piston rods 38 and 39 of the belt actuating rams 42 and 43. The piston rods 38 and 39 as shown in this view are fully projected, whereby the pawl 36 of piston rod 38 will have operatively engaged and partially rotated ratchet wheel 35 to drive the belt 10 through the first half of its motion. The pawl 37, being arranged to act only on the downward movement of its associated piston rod 39, will remain inoperative at this time.

As continued rotation of the crank wheel 88 causes the bar 85 to commence its return reciprocation toward the right, the toothed rack segment 84a will first actuate the pinion 84 to reverse valve 47 and retract the piston rods 38 and 39. During its downward retraction the pawl 37 will then operatively engage ratchet wheel 35 -to complete the movement of the belt 10. The teeth of the ratchet wheel 35 are so spaced `and the throw of the piston rods 38 and 39 is of such extent that each complete movement of the belt 10 will be equal to the distance between the centers of adjoining boxes 33. Thus during each movement of the belt, the area of the belt overlying each box 33 will advance toward the right to a position for cooperation with the next succeeding box 33.

Further movement of the rack bar 85 toward the right as the belt 10 dwells in stationary position will cause the rack segment 83a to engage pinion 83 and actuate the valve 78 to cause the ram 72 and its associated mechanism to raise the suction boxes 33 into engagement with the belt run 10a. Still further movement of the bar 85 toward the right and the ensuing cooperation of rack segment 82a with pinion 82 will then position the valve 60 to transmit suction to the boxes through lines 63. In Figure 6, the rack bar 85 is shown in its right hand position after having completed the positioning of the Valves in this manner. The suction will then be continuously applied to the lower surface of the belt run 10a during subsequent moa/ement of the rack bar 85 to the right to the position of Fig. 6, and until it has returned again to the left sufficiently to operatively engage the rack segment 82a with its cooperating pinion 82 and again position the valve 60 to release the suction by venting the several boxes to the atmosphere. After the boxes 33 are thus vented to permit their withdrawal from the belt run 10a, the rack segment 83a then actuates the valve 78 to retract the boxes from the sealing engagement with the belt run, and it is only after these two steps have been 'l completed that.' the', rack' segment f 84ay acts through pinion 84-toinstitute the next stage of movement of the belt 10;

Thus in the overall operation ofy the apparatus: it will be apparent thaty the filter cake deposited on the lowermost box33V at the left hand: end off the belt run 10a will be'successively positioned over each of the suction boxes 33 during the successive movements of thebelt run 10a to the right. DuringY the dwelliofthefilter cake over each such box, suction applied through they belt will act to draw at least a portionY of the liquid from the filter cake downwardly through the belt and. into4 the box so that by the time the filter calce passes aroundthe roller 12 it will contain but a minimum amountof liquid, and-will either be broken loose from the.belt for` discharge: by the bending of' the belt as. the -latter passes around the roller 12 or, if thisbending action does notV suffice to remove all of the material, the scraper bladesl` will function to complete its removal;

It will be further apparent that due to the disengagement ofthe boxes fromlthe beltY and/ or to the release of the suction during the intermittent movements of the belt, there will be a minimum4V amount of wearv on the box seals 34 and these in turn will be operative to maintain a sealing engagement with the belt over a long-period of time. Moreover, this will result in reduced power requirements for moving the belt.

Having thus described my invention, I claim:

l. A ltering unitcomprising an endless filter belt having an operative generally horizontal run disposed to present upper and lower surfaces, whereby material to be filtered may be deposited` on said upper surface, means supporting and guiding said belt for movement through an endless circuit, intermittent drive mechanism operatively associated with said belt for alternately moving said belt along its said circuit and permitting it to remain at rest for predetermined intervals, abox having an open side presented toward thelower surface ofthe belt, and means mounting saidbox` whol-ly'beneath'said belt for -vertical movement to and from a position of sealing engagement with saidy belt wherein said lower surface of the belt covers and seals the open side of the box, mechanism coordinated with said intermittent drive mechanism for moving said box to and from sealing relation with said belt as the belt comesto restand upon its resumption of movement respectively, and' pneumatic means connected to said box forV modifying the airpressure within said box in coordination with the movements of said belt by reducing Isaid air pressure belowv atmospheric pressure each time-the belt comes to rest and by raisingl said pressure to atmospheric pressure just prior to resumption of eachbelt movement.

2. A filtering unit comprising an endless filter belt having an operative generally horizontalV run presenting upper and lower surfacesboth exposed to air pressure, whereby material to be tiltered may be deposited on said upper surface, and means supporting said belt for movement-through an endless circuit, intermittent drive mechanism operatively connected to said supporting means for alternately moving said belt along its said circuit and permitting it to remain at rest for predetermined intervals, a box having an open side presented toward the lower surface of said belt, said side being normally open to atmospheric pressure, andrneans mounting said box wholly beneath said operative run for vertical movement to and from a position of-sealing engagement with said belt wherein said lower surface of the operative run covers andseals the open side of the box, mechanism coordinated with said intermittent drive mechanism for vertically moving said box to and from a position of sealing engagement wherein said lower surface of the belt covers and seals the open side of the box, mechanism coordinatedl with said intermittent drive mechanism for moving said box into such sealing engagement when the beit comes to rest and for moving said box from such sealing engagement prior to resumption ofthe-movement of the'` belt, pneumatic means connected to said box and coordinated with said intermittent drive mechanism for reducing the' air pressure within the box below atmospheric pressure while the belt is' at rest and for admitting air at atmospheric pressure to said box prior to the resumption of the movement of said belt.

3. A filtering unit comprising an endless filter belt having a generally horizontal operative run, whereby material to be filtered may be deposited on the upper surface of said run,- means supporting and guiding said belt for movement through an endless circuit, intermittent drive mechanism operatively associated with said belt for alternately moving said belt along said circuit and permitting it to remain at rest for predetermined intervals, a suction box disposed wholly beneath said operative runof the belt and having an open upper side presented toward the lower surface of said nm and means mounting said box for vertical4 movement to and from a position of sealing engagement with said belt wherein said:Y lower surface of the belt run covers and seals said open upper side ofthe box, mechanism coordinated with said intermittent drive mechanism for vertically moving said boxv to and-from such sealing relation as the belt comes to rest and upon its resumption of movement respectively, means communiacting with said box for evacuating air therefrom, means including a valve, and valve operating mechanism coordinated with said drive mechanism for venting said box to the atmosphere prior to each movement of the box from sealing engagement with the operative belt run, and means above said run and out of a vertical registry with said box for applying material to be filtered onto said run.

4. A filtering unit comprising an` endless filter belt having a generally horizontal filtering run, means supporting and guiding said belt for movement through an endless circuit, a plurality of boxes below said filtering run disposed at uniformly spaced intervals along said run, each said box having an open side presented toward said run, means mounting the respective boxes for vertical movement to and from positions of sealing engagement with the belt wherein said filtering run covers and seals the open sides of the respective boxes, intermittent drive mechanism operatively associated with said belt for intermittently moving said belt through uniform movements along saidcircuit, each equal to the distance between centers of adjoining boxes, whereby a given area on said belt which registers with the first in order of said boxes with regard to the direction of belt movement will register successively with the respective boxes, mechanism coordinated with said intermittent drive mechanism for moving said boxes'to and from sealing relation with the beltV as the belt comes to rest and before it resumes movement respectively, and pneumatic means connected to said boxes and operating in coordination with said movement of the boxes for reducing the air pressures in said boxes coincident with said sealing engagement of said boxes with the belt and for admitting air at atmospheric pressure into said boxes before the boxes are moved out of said sealing engagement.

5. The combination of claim 4 including a feed hopper vertically opposed to the said first in order of the said boxes for supporting a mixture of liquid and solid materials in engagement with the upper surface of said belt filtering run, to form a coat of filtered material thereon, the areay immediately above said run and over the balance of said boxes being'free and unobstructed to avoid displacement'of said coat as same moves over successive boxes.

6. The combination of claim 6 wherein said means mounting the respective boxes and the filtering run for relative vertical movement comprises a rigid stationary framey supporting saidfilter belt, and a rigid movable frame guided for generally vertical movement on said stationary frame, the said boxes being carried by said movable frame, and said mechanism for relatively moving said boxes and filtering run is interconnected between the respective frames to cause operative vertical movement ofthe movable frame.

7. The combination of claim 4 wherein said pneumatic means comprises a header connected to all of said boxes, air supply and exhaust passages respectively communieating with said header, and a valve alternately operable to establish communication between the header and said respective passages.

8. The combination of claim 7 including air evacuating means communicating with said air exhaust passage, the air supply passage communicating with the atmosphere.

9. A ltering unit comprising an endless filter belt having a generally horizontal operative iilter run, whereby material to be iiltered may be deposited on the upper surface of said run, means `supporting and guiding said belt for movement through an endless circuit, a plurality of suction boxes beneath said operative run disposed at uniformly spaced intervals along said run, each said box having an open upper side presented toward said run, means mounting the respective boxes and the said operative run for relative vertical movement to and from positions of sealing engagement wherein said operative run covers and seals the open sides of the respective boxes, intermittent drive mechanism operatively assoicated with said belt for moving the belt at spaced intervals of time in uniform intermittent steps, each equal to the distance between centers of adjoining boxes, whereby the same areas on the belt will register successively with and successively close the respective boxes, mechanism coordinated with said intermittent drive mechanism for relatively moving said boxes and said operative run to and from sealing relation each time the belt cornes to rest and before it resumes movement respetcively, air evacuation means connected to the respective suction boxes, and means coordinated with said intermittent drive mechanism for venting said boxes to the atmosphere prior to each movement of the belt.

10. The combination of claim 9 including a feed hopper located over said operative run and generally in vertical registry with one of said suction boxes, said hopper having an open bottom in sealing engagement with said operative run, whereby the hopper may maintain a mixture of liquid and solid materials on said run above said suction box.

1l. A filtering unit comprising an endless lter belt having a generally horizontal operative lter run, whereby material to be filtered may be disposed on the upper surface of said run, a stationary frame having rollers thereon supporting and guiding said belt for movement through an endless circuit, a movable frame guided for generally vertical movement on said stationary frame, a plurality of suction boxes carried by said movable frame beneath said operative run and disposed at uniformly spaced intervals along said run, each said box having an open upper side presented toward said run, intermittent drive mechanism operatively associated with said belt for moving the belt intermittently in uniform steps at spaced time intervals, each step equalling the distance between centers of adjoining boxes, whereby the same areas on the belt will register successively with the respective boxes, mechanism interconnected between said stationary frame and said movable frame and operating between successive movements of the belt to raise said movable frame and bring the open sides of said boxes into sealing engagement with said operative run and then to lower said movable frame and retract said boxes from the operative run, air evacuating means connected to the respective boxes, and means for venting said boxes to the atmosphere during movements of the belt.

12. A iiltering unit comprising an endless filter belt having an operative horizontal iiltering run, means supporting and guiding said belt for movement through an endless circuit, apparatus disposed wholly beneath said iiltering run for simultaneously applying suction to a plurality of similarly shaped relatively uniformly spaced areas along said run, means for intermittently moving said apparatus into and out of operative engagement with the run, intermittent driving means for said belt operative each time said suction applying apparatus is disengaged from the run to move said belt a distance along said circuit corresponding to the distances between centers of :said areas, whereby each such area will be repeatedly engaged by said apparatus, and means actuating said suction applying apparatus to relieve the suction on said belt ltering run prior to each movement of the apparatus out of operative engagement with the run.

References Cited in the le of this patent UNITED STATES PATENTS 920,909 Brewer May 11, 1909 935,359 Diver Sept. 28, 1909 1,201,021 Callow Oct. 10, 1916 1,403,369 Anderson Jan. 10, 1922 1,933,370 Dotterweich Oct. 31, 1933 2,570,697 Nordengren Oct. 9, 1951 2,665,812 Crane Jan. 12, 1954 2,675,129 Doubleday Apr. 13, 1954 

